Afghan officials said Thursday that they had decided to postpone the country's presidential election until August, saying they needed more time to prepare. But the decision, which appeared to contravene Afghanistan's Constitution, raised questions about the legitimacy of what could be President Hamid Karzai's final months in office.

But Afghanistan's Constitution states that the president's term expires on the equivalent of May 22 on the Roman calendar. Presidential elections, the Constitution says, must be held 30 to 60 days before the end of the term.

The Obama administration has picked Lt. Gen. Karl W. Eikenberry, a former top military commander in Afghanistan, to be the next United States ambassador to Kabul, an administration official said Thursday. Tapping a career Army officer who will soon retire from the service to fill one of the country's most sensitive diplomatic jobs is a highly unusual choice.

But Afghanistan specialists say that General Eikenberry, who served in Afghanistan twice, including an 18-month command tour that ended in 2007, knows the players and issues there well. That is a valuable commodity in a year when the United States will send thousands of additional troops to Afghanistan and the country will hold presidential elections.

The Australian Defence Force has enough spare capacity to boost its military contribution in Afghanistan, but any increase would be meaningless unless matched by other NATO nations, counter-insurgency expert, retired Major-General Jim Molan said yesterday.

Afghanistan was discussed in a 25-minute phone call to Kevin Rudd from US President Barack Obama yesterday, but there was no request for Canberra to boost its troop commitment to the understrength 55,000-strong NATO-led International Security Assistance Force there.

The ADF has 1000 troops deployed, including a 300-strong Special Forces Task Group targeting insurgents.

Britain's top military commander has admitted for the first time that America was right to criticise the way in which British troops carried out counter-insurgency operations against the Taleban in southern Afghanistan when they first deployed to Helmand province in 2006. Air Chief Marshal Sir Jock Stirrup, the Chief of the Defence Staff and a former head of the RAF, blamed commanders for being "smug and complacent" about the challenges they faced in Helmand.

His words echoed accusations made by Robert Gates, the US Defence Secretary, and several senior American military officers who claimed that their British counterparts spent too much time boasting about their experiences in Northern Ireland.